1. Field of the Invention
The invention relates to a method for controlling the movement of a transportation unit of a conveying device in the form of a long-stator linear motor, wherein the transportation unit is moved along a conveying line and the conveying line is composed of a number of conveying segments.
2. Discussion of Background Information
The invention relates to a conveying device in the form of a long-stator linear motor, in which a multiplicity of transport units is moved along a defined conveying line. A multiplicity of driving coils is arranged along the conveying line, which driving coils can be individually actuated in order to generate a moving magnetic field. The moving magnetic field cooperates with exciting magnets, generally permanent magnets, on a transportation unit so as to move the transportation unit in accordance with the motor principle. Such conveying devices have long been known, for example from U.S. Pat. No. 8,996,161 B2.
The movement profile of a transportation unit is planned in advance so as to accurately determine how the transportation unit shall move (for example position, speed, acceleration). In the case of a conveying device in the form of a long-stator linear motor, this can be rather complex, since a very large number of transportation units are generally moved simultaneously and the conveying line can comprise complex geometries, also including a number of line sections.
A conveying device generally consists of conveying segments which each comprise a number of driving coils, which are each controlled by an associated segment controller. The conveying segments are arranged adjacently so as to form the conveying line. A movement profile for a transportation unit, however, is normally planned over a number of conveying segments, and therefore a segment controller also has to implement just part of the movement profile. Only the relevant part of the movement profile can thus be transferred to each segment controller in order to control the transportation unit through the associated conveying segment. This, however, is very complex, in particular with a very large number of transportation units. Regardless of this, there are also specifications for the movement of the transportation unit with regard to the continuity of the movement. For example, acceleration jumps are undesirable and even must be frequently avoided. The planning of short movement profile sections, which are linked to one another and which are each controlled by different segment controllers in order to together give the overall movement profile, is also very complex, however, and is very difficult to realize.
U.S. Pat. No. 8,996,161 B2 describes a control architecture with which any drive axis can be controlled, in particular also a drive axis of a conveying device in the form of a long-stator linear motor having a series of conveying segments. Here, a movement profile for a drive axis (transportation unit) is planned by a user and the movement profile is then transferred to a control unit, which converts the movement profile into control commands for the corresponding driving coils of the conveying segments. The movement profile is planned here over a number of conveying segments and therefore does not have to be planned for individual conveying segments. The control unit ensures the implementation of the movement profile over the conveying segments. The movement profile is planned by means of standard software for any drive axes, wherein the specific implementation of the conveying line is also taken into consideration in the planning. The created movement profile for a transportation unit is thus linked to an implementation of the conveying line. Due to the identification of the conveying line, the control unit can then convert the movement profile over the conveying line into a movement of the transportation unit. This type of control architecture indeed facilitates the planning of the movement profile, because there is no longer any need for specific software, however it is still complex, since each drive axis must be planned separately in the specific implementation of the respective drive axes.